Whipping up the winds of Jupiter in the lab
Jupiter isn't just the largest planet in our Solar System, it's a giant enigma. To gain a better understanding of the secrets wrapped in the planet's envelope of gas and storms, scientists from the US and France have built a miniature "tabletop" Jupiter that provides an analog simulation of the Jovian atmosphere's deep structure and internal dynamics.
Ever since modern telescopes and deep space probes provided better views of Jupiter, scientists have been striving to gain a better understanding of how the gas giant is put together and why it functions the way it does. One prominent feature of the tens of thousands of miles thick atmosphere are the colorful bands that encircle the planet, which are driven by winds that howl at near-supersonic velocities.
One of the big questions is, do these swirling winds or "jets" exist only in Jupiter's upper atmosphere, or do they extend down into the deep structure of the lower altitudes? So far, scientists have relied on surface images and measurements combined with computer simulations, but these have proven less than satisfactory. Led by UCLA geophysicist Jonathan Aurnou, the team's new approach is to create an analog model of Jupiter that reproduces the Jovian atmosphere on a lab bench.
According to UCLA, the tricky bit of the analog simulator was to find a way of reproducing three key attributes of the Jovian atmosphere in the laboratory: rapid rotation, turbulence, and the spherical shape of Jupiter. Previous attempts had failed to produce decent jets because the apparatus couldn't spin the models fast enough or generate enough turbulence.
Aurnou's team constructed a table on air bearings that can spin at 120 rpm and support 1,000 kg (2,200 lb). This was enough to hold a 200 liter (105 gal) industrial-sized garbage can full of liquid that, when spun at up to 75 rpm, bent into a parabola that approximated the Jovian atmosphere.
The researchers then uses a pump under the false floor to inject colored water through a series of inlet and outlet holes to generate turbulence. The result was that in minutes the spinning tank showed six concentric flow rings going in opposite directions – the first time such Jovian flows had been reproduced in the laboratory. In addition, because they were injected in the bottom of the tank and appeared on the surface, the scientists infer that there are deep-diving jets on Jupiter.
The next step will be to compare the results with data being sent back by NASA's Juno probe, which is currently orbiting Jupiter and carries instruments specifically designed to look at the planet's deep structure. In addition, the team will be using supercomputers at Argonne National Laboratory to gain a more detailed insight into Jupiter's structure and dynamics, and will attempt to simulate a stable layer of fluid on top of the spinning water in the tank to represent the outer layer of Jupiter's atmosphere.
"The Juno data from the very first flyby of Jupiter showed that structures of ammonia gas extended over 60 miles into Jupiter's interior, which was a big shock to the Juno science team," says Aurnou. "UCLA researchers will be playing an important role in explaining the data."
The research is published in Nature Physics.